In minimally invasive surgical (MIS) procedures, elongated illuminators and viewers, i.e., laparoscopes and endoscopes, are inserted through small incisions in the abdominal wall or elsewhere. The viewer is typically coupled to a video camera that shows the operating field on a monitor.
A common problem is that the lens on the viewer becomes fogged. When the viewer is inserted, the lens is typically at operating room temperature which is often much colder than room temperature. The body cavity is at body temperature and high humidity. As such, water droplets condense on the lens, obscuring the view. When the lens fogs, the surgeon must remove the instrument, clean the lens, and reinsert the instrument at which time fogging often begins again.
To address this problem, the instrument may be immersed in a warm saline bath before surgery and during cleaning. This can be time-consuming and it is difficult to control temperature to consistent, effective working temperature.
An automated approach is described in Published U.S. Patent Application 2002/0022762 A1. A lens warming and cleaning device for use with an optical surgical instrument is disclosed. The device includes a heat-conducting tube sized and shaped to receive the lens portion of the instrument, a heating element thermally coupled to an exterior of the tube, and a cleaning member disposed within the tube. The cleaning member is disposed such that when the lens portion of the instrument is inserted into the tube, the lens portion contacts the cleaning member.
The heating element comprises a flexible pad that surrounds at least a portion of the tube including the lens portion. The pad may be wrapped around tube or attached to tube using an adhesive or hook-and-loop fasteners.
In one disclosed embodiment, the heating pad includes a flexible, air-permeable outer bag that encases a chemical mixture that generates an exothermic reaction when activated. The chemical mixture can be, e.g., a mixture of iron powder, water, cellulose, vermiculite, activated carbon, and salt. Exposing the mixture to atmospheric oxygen triggers an exothermic reaction that warms the pad to a temperature of about 60° C. and sustains that temperature for about six hours.
Other types of known exothermic reaction mixtures can be used. For example, the mixture can consist of iron powder, a chloride or sulfate of a metal having a tendency of ionization greater than iron, active carbon, and water. Alternatively, the chemical mixture can be a super-cooled, supersaturated aqueous solution of sodium acetate. The pad can also employ other types of exothermic chemical reactions to generate heat, or it can include a resistance heater powered by, e.g., a battery or an external source of electricity.
The problems with this system are two-fold. First, the addition of a cleaning mechanism is all embodiments constitutes an unnecessary complication, since warming is by far the greatest need. Additionally, although “other types of exothermic chemical reactions” are mentioned in passing, activation methods and apparatus are not disclosed. Accordingly, the need remains for a less expensive yet effective endoscope/laparoscope warming system.